linux-kernel - [PATCH] um: Prevent KASAN splats in dump

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Message-ID: <20220907100533.1719128-1-vincent.whitchurch@axis.com>
Date:   Wed, 7 Sep 2022 12:05:33 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>
CC:     <kernel@...s.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Patricia Alfonso <trishalfonso@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        <linux-um@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] um: Prevent KASAN splats in dump_stack()

Use READ_ONCE_NOCHECK() when reading the stack to prevent KASAN splats
when dump_stack() is used.

Fixes: 5b301409e8bc5d7fad ("UML: add support for KASAN under x86_64")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
 arch/um/kernel/sysrq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/um/kernel/sysrq.c b/arch/um/kernel/sysrq.c
index 7452f70d50d0..746715379f12 100644
--- a/arch/um/kernel/sysrq.c
+++ b/arch/um/kernel/sysrq.c
@@ -48,7 +48,8 @@ void show_stack(struct task_struct *task, unsigned long *stack,
 			break;
 		if (i && ((i % STACKSLOTS_PER_LINE) == 0))
 			pr_cont("\n");
-		pr_cont(" %08lx", *stack++);
+		pr_cont(" %08lx", READ_ONCE_NOCHECK(*stack));
+		stack++;
 	}
 
 	printk("%sCall Trace:\n", loglvl);
-- 
2.34.1